(a) Field of the Invention
The present invention relates to a back sheet, a method of manufacturing the same, a solar cell module using the same and a method of manufacturing the solar cell module.
(b) Description of the Related Art
Recently, necessity of clean alternative energy is growing due to depletion of fossil fuels and global warming by carbon dioxide. Therefore, various alternative energy sources such as wind power, bio-gas, hydrogen fuel cell, nuclear power, solar heat, geothermal heat, and so on are being developed. A solar cell using solar energy is one of the alternative energy sources.
Generally, a solar cell module includes a substrate made of glass or glass-like material, a solar cell, an encapsulation, and a protective sheet for a back surface (back sheet).
Since one solar cell cannot output sufficient power, a plurality of solar cells are disposed in series or parallel on the substrate and are electrically connected to each other so as to form one solar cell module. In addition, the back sheet is bonded to the encapsulation for attaching the solar cells at a back surface of the solar cell module and protects the solar cell module against physical impact from external environment or water and contaminant.
Generally, sunlight projected into the solar cell module is reflected at the back sheet between one solar cell and another solar cell and is totally reflected toward the substrate so as to be transmitted to the solar cell. Therefore, back sheet is required to have high reflectivity in order to increase power capacitance of the solar cell module under predetermined dimensions.
A conventional back sheet is made of milky white material in order to increase reflectivity of the back sheet used in the solar cell module. In addition, content of titanium dioxide may be adjusted or a light diffusion layer or a light reflection layer is formed on a surface of the back sheet in order to increase reflectivity.
However, increase of content of titanium dioxide in the back sheet is limited due to physical properties. In addition, if the light diffusion layer or the light reflection layer is formed, durability of the back sheet may be deteriorated or manufacturing cost may increase.
It is disclosed in Japanese Patent Laid-Open Publication No. 2006-319250 that a back sheet for a solar cell includes a light diffusion layer having a fine convex portion or a fine recess portion and a metal deposit layer having reflectivity and gas barrier. However, Japanese Patent Laid-Open Publication No. 2006-319250 has problems of high manufacturing cost and requiring high-technology in order to form the light diffusion layer having the fine convex portion or the fine recess portion.
In a case that the solar cell module is located in a desert area where there are a lot of sunlight, a lot of power can be produced.
However, cycle-life of the solar cell module is short and cost for maintaining and replacing the solar cell module is high in the desert area because much ultraviolet rays are irradiated, midday temperature is very high, temperature difference between day and night is very large, and sandblast damages the solar cell module. Therefore, cost performance of the solar cell module is very low.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.